CN107071785A - The frequency spectrum distributing method of cognition wireless network is relayed a kind of cooperation more - Google Patents

Abstract

The invention relates to a spectrum allocation method for a cooperative multi-relay cognitive wireless network. Relying on the cooperative relay cognitive wireless network, a secondary user can improve its spectrum access opportunities by assisting a primary user in data transmission, and further improve the capacity of the cognitive network system. . According to the actual working condition of the channel and the data transmission requirements of the main user, the present invention reasonably selects multiple relay paths and optimally allocates the channels to obtain the maximum cognitive network capacity. The present invention achieves the purpose of improving the throughput of the cognitive network in the multi-relay cooperative system by adopting the above means.

Description

A Spectrum Allocation Method for Cooperative Multi-Relay Cognitive Wireless Networks

technical field

The present invention relates to multi-relay cooperative communication technology in the field of wireless communication network, and more specifically relates to a cooperative relay selection, channel allocation and power allocation method in the cognitive wireless channel environment.

Background technique

With the rapid development of wireless communication services, the contradiction between the ever-increasing spectrum demand and the increasingly scarce spectrum resources is becoming more and more prominent. Introducing cognitive technology and cooperative relay into wireless network can effectively solve this contradiction, and cooperative relay cognitive wireless network has been favored by people.

In cognitive wireless networks, secondary users (cognitive users) can occupy channels not occupied by primary users (authorized users). In order to increase the capacity of the secondary user network and obtain the maximum network throughput, cognitive users should utilize as much idle spectrum as possible. Existing cognitive technologies generally adopt a non-relay method, and secondary users occupy the system spectrum when the spectrum is free by detecting the occupancy state of the primary user.

When the fading of the communication channel is large, cooperative relay is beneficial to improve the system performance. In cooperative relay cognitive radio networks, secondary users usually act as relay nodes. Relay nodes can act both as relays between secondary user communications and as relays for primary users. As the primary user relay, the secondary user can increase the transmission rate of the primary user and save the transmission time of the primary user, thereby increasing the opportunity for the secondary user to use the system spectrum and improving the transmission capacity of the secondary user. However, how to reasonably select relays, and how to allocate spectrum resources and power to obtain the maximum network throughput has become a major problem in the spectrum allocation of cooperative multi-relay cognitive wireless networks.

Contents of the invention

In order to overcome the deficiencies of the above-mentioned existing technologies and solve the problem of spectrum allocation in cooperative multi-relay cognitive wireless networks, the present invention proposes a spectrum allocation method for cooperative multi-relay cognitive networks with maximum throughput. According to the channel of the network system According to the situation and the rate requirements of the primary user, the relay set, channel allocation and power allocation are reasonably selected to maximize the system capacity.

In order to achieve the above object, the method for allocating time slots in a cooperative relay cognitive wireless network of the present invention includes the following steps:

Step 1, network system configuration, in the cooperative multi-relay cognitive network, there is a primary user transmitter PT, a primary user receiver PR, and L secondary user pairs, and each secondary user pair is controlled by the secondary user transmitter ST and the secondary user receiver SR, the set is represented by L, the normalized spectral bandwidth of the multi-relay cognitive network is B, the number of sub-channels is N, and the set of sub-channels is N, then the sub-channel bandwidth B ₀ =B/N , the secondary user uses adaptive modulation for data transmission, and the data transmission rate is automatically adjusted according to the quality of the channel;

Step 2, system parameter setting, under this system, the transmission power of the primary user transmitter PT on each sub-channel is a fixed value P _pu , the total transmission power of the secondary user system is P _su , the primary user transmitter PT and the secondary user system The channel gains on channel n between the user transmitter ST, the secondary user transmitter ST and the primary user receiver PR, and the secondary user transmitter ST and the secondary user receiver SR are defined as with The channel noise has a mean of 0 and a variance of Gaussian white noise, the target rate of the primary user is R _T ;

Step 3, relay selection and channel allocation, the specific steps are as follows:

a1. Calculate the communication rate between the primary user transmitter PT and the secondary user transmitter ST _l on the nth channel Its calculation is as follows:

Define the ratio of the communication rate of the primary user and the secondary user transmitter ST _l on the nth channel to the target rate of the primary user as the performance evaluation parameter for relay selection and channel allocation:

Thus, the performance evaluation parameter matrix of the relay cognitive wireless network is obtained:

Define parameter β _sum = 0;

a2. Select the maximum value in the performance evaluation parameter matrix

The corresponding secondary user is used as the optimal relay, and the corresponding channel is used as the optimal channel, that is, the primary user selects ST _l' as the relay and occupies channel n' for data transmission;

a3. Update β _sum ,

Since a channel can only be occupied by one user at a time, the optimal channel n' no longer participates in the secondary user channel selection below, that is,

a4. Cycle a2 and a3 until β _sum ≥ 1, that is, meet the primary user rate requirement;

Step 4, sub-channel allocation of the first time slot. In step 3, the primary user can release the unoccupied channel under the condition of satisfying its own rate requirements, and the secondary user can occupy the channel not occupied by the primary user for data processing. Transmission, under this allocation method, in order to reflect the fairness among users, only the relay secondary users participating in the cooperation are allowed to occupy the remaining channels for their own data transmission in the first time slot. Assuming that the relay set is L*, the number of is L*, and the set of remaining channels is The number is The corresponding channel gain matrix can be expressed as

Define the performance parameters of the l ^* th secondary user pair:

The performance matrix can be obtained as follows:

Use the Hungarian algorithm to obtain the optimal channel allocation scheme. Since the Hungarian algorithm solves the square matrix problem, when the remaining channels and the number of users are different, a square matrix needs to be constructed. At this time, there are two situations:

b1. When the number of remaining channels is less than the number of users, a virtual channel needs to be constructed, and the channel gain is set to 0, namely:

b2. When the number of remaining channels is greater than the number of users, it is necessary to construct virtual users. The maximum number of channels that each user may occupy is The performance matrix is constructed as follows:

The 5th step, power distribution of the first time slot, according to the number of remaining channels occupied by each relay distributes the transmission power, and the secondary user transmitter ST _1* gets the power as follows:

in, Indicates the occupancy of the channel n by the secondary user transmitter ST ₁ in the first time slot. When it is occupied, the value is 1, otherwise it is 0. Use the water filling algorithm to calculate the power of the secondary user transmitter participating in the relay on each occupied channel distribute;

In the 6th step, in the second time slot, the secondary user transmitter as a relay forwards the primary user data to the primary user receiver, and all secondary user transmitters send their own transmission data to the secondary user receiver.

For the water filling algorithm, please refer to the literature: Q.Qi, A.Minturn, and Y.Yang.An Efficient Water-Filling Algorithm for Power Allocation in OFDM-Based Cognitive Radio Systems.InProc.2012 International Conference on Systems and Informatics(ICSAI 2012),pp. 2069-2073, 2012.

The present invention also has following further features:

1. The sixth step specifically includes the following steps:

c1. In the second time slot, the channel for forwarding the primary user signal is selected and the transmission power of the occupied channel is allocated. The channel for the relay forwarding the primary user signal can be the same as that of the primary user in the first time slot to the relay node The channels for transmitting signals are different. In the first time slot, the secondary user transmitter that is preferentially selected as the relay has the channel n” with the largest channel gain as the channel occupied when forwarding the signal to the primary user receiver PR in the second time slot. , calculate the transmission power required by the secondary user transmitter ST _l* as a relay to forward the primary user in the second time slot

c2, the second time slot channel allocation, in this time slot, each user transmitter can occupy the idle sub-channel, also use the Hungarian algorithm to obtain the optimal channel allocation scheme, and when the number of channels is different from the number of users, It is necessary to construct a square matrix for channel allocation;

c3, the power distribution of the second time slot, the transmission power of the secondary user transmitter ST1 _" to the secondary user receiver in the second time slot is as follows:

in Represent the occupancy of channel n by the secondary user transmitter ST ₁ in the second time slot, and equally utilize the water filling algorithm to obtain the power allocated by the secondary user transmitter in this time slot on each channel;

c4. Perform resource allocation according to channel and power allocation conditions of the two time slots, and complete data transmission.

2. In step 3, the selection of the relay depends on the performance evaluation parameters Its magnitude depends on the target rate of the primary user as R _T , the transmit power of the primary user P _pu , and the channel gain between the primary user transmitter and the secondary user transmitter and noise power

3. In step 4, the Hungarian algorithm is used for the allocation of the remaining channels, and the value of its parameter depends on the channel gain between the secondary user transmitter and receiver, and its parameter is defined as in Equation 7.

5. The allocation of the remaining power depends on the ratio of the number of allocated channels to the total channels occupied by the secondary user system.

The invention relies on the cooperative multi-relay cognitive wireless network, and the secondary user increases the transmission rate of the primary user through the data transmission of the primary user through cooperation, and obtains more spectrum resources, thereby increasing the channel capacity. According to the speed requirement of the primary user, the present invention reasonably selects multiple relay sets to obtain the maximum cognitive network capacity. The present invention adopts the above means to realize a multi-relay cooperative system and achieve the purpose of improving the throughput of the cognitive network.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram of a cooperative multi-relay cognitive radio network.

Fig. 2 is a flowchart of frequency spectrum allocation according to an embodiment of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Figure 1 is a schematic diagram of a cooperative multi-relay cognitive radio network in this embodiment. It can be seen from the figure that the network has a primary user transmitter PT, a primary user receiver PR, and L secondary user pairs (transmitters ST and secondary user receiver SR), the secondary user uses adaptive modulation for data transmission, and the data transmission rate is automatically adjusted according to the quality of the channel.

In the assisted relay model, the data forwarding cycle includes two phases (time slots), the phase of sending data from the primary user to the secondary user and the phase of forwarding the data of the primary user by the secondary user. In each phase, secondary users can occupy channels not occupied by primary users. Therefore, there are channel allocation and power allocation issues at each stage.

The present invention implements a cooperative multi-relay cognitive radio network spectrum allocation method (see Figure 2 for the flowchart), comprising the following steps:

Step 1, network system configuration, in the cooperative multi-relay cognitive network, there is a primary user transmitter PT, a primary user receiver PR, and L secondary user pairs, and each secondary user pair is controlled by the secondary user transmitter ST and the secondary user receiver SR, and the set is denoted by L. The normalized spectral bandwidth of the multi-relay cognitive network is B, the number of sub-channels is N, and the set of sub-channels is N, then the sub-channel bandwidth B ₀ =B/N. The secondary user uses adaptive modulation for data transmission, and the data transmission rate is automatically adjusted according to the quality of the channel. In this embodiment, the primary user bandwidth is B=160MHz, L=4, N=16;

Step 2, system parameter setting, under this system, the transmission power of the primary user transmitter PT on each sub-channel is a fixed value P _pu , the total transmission power of the secondary user system is P _su , the primary user transmitter PT and the secondary user system The channel gains on channel n between the user transmitter ST, the secondary user transmitter ST and the primary user receiver PR, and the secondary user transmitter ST and the secondary user receiver SR are defined as with The channel noise has a mean of 0 and a variance of Gaussian white noise, the target rate of the primary user is R _T . In this example: noise variance The transmitter power P _pu of the primary user on each subchannel = 20mW, and the target rate R _T of the primary user = 1bit/s/Hz;

Step 3, relay selection and channel allocation, the specific steps are as follows:

a1. Calculate the communication rate between the primary user transmitter PT and the secondary user transmitter ST _l on the nth channel Its calculation is as follows:

Define the ratio of the communication rate of the primary user and the secondary user transmitter ST _l on the nth channel to the target rate of the primary user as the performance evaluation parameter for relay selection and channel allocation:

Thus, the performance evaluation parameter matrix of the relay cognitive wireless network is obtained:

Define parameter β _sum = 0;

a2. Select the maximum value in the performance evaluation parameter matrix

The corresponding secondary user is used as the optimal relay, and the corresponding channel is used as the optimal channel, that is, the primary user selects ST _l ' as the relay and occupies channel n' for data transmission;

a3. Update β _sum ,

Since a channel can only be occupied by one user at a time, the optimal channel n' no longer participates in the secondary user channel selection below, that is,

a4. Cycle a2 and a3 until β _sum ≥ 1, that is, meet the primary user rate requirement;

Step 4, sub-channel allocation of the first time slot. In step 3, the primary user can release the unoccupied channel under the condition of satisfying its own rate requirements, and the secondary user can occupy the channel not occupied by the primary user for data processing. Transmission, under this allocation method, in order to reflect the fairness among users, only the relay secondary users participating in the cooperation are allowed to occupy the remaining channels for their own data transmission in the first time slot. Assuming that the relay set is L*, the number of is L*, and the set of remaining channels is The number is The corresponding channel gain matrix can be expressed as

Define the performance parameters of the l ^* th secondary user pair:

The performance matrix can be obtained as follows:

Use the Hungarian algorithm to obtain the optimal channel allocation scheme. Since the Hungarian algorithm solves the square matrix problem, when the remaining channels and the number of users are different, a square matrix needs to be constructed. At this time, there are two situations:

b1. When the number of remaining channels is less than the number of users, a virtual channel needs to be constructed, and the channel gain is set to 0, namely:

b2. When the number of remaining channels is greater than the number of users, it is necessary to construct virtual users. The maximum number of channels that each user may occupy is The performance matrix is constructed as follows:

The 5th step, power distribution of the first time slot, according to the number of remaining channels occupied by each relay distributes the transmission power, and the secondary user transmitter ST _1* gets the power as follows:

in, Indicates the occupancy of the channel n by the secondary user transmitter ST ₁ in the first time slot. When it is occupied, the value is 1, otherwise it is 0. Use the water filling algorithm to calculate the power of the secondary user transmitter participating in the relay on each occupied channel distribute;

Step 6, in the second time slot, select the channel for forwarding the primary user signal and allocate the transmission power of the occupied channel, and the channel for relaying the primary user signal can be in the same direction as the primary user in the first time slot. The channels used by relay nodes to transmit signals are different, and the secondary user transmitter that is preferentially selected as the relay in the first time slot has the priority to select the channel n” with the largest channel gain as the second time slot to occupy when forwarding the signal to the primary user receiver PR channel, calculate the transmit power required by the secondary user transmitter ST _l* as a relay to forward the primary user in the second time slot

The 7th step, channel assignment of the second time slot, in this time slot, each user transmitter can occupy the idle sub-channel, utilize the Hungarian algorithm equally, obtain optimal channel allocation scheme, when the number of channels and the number of users are different At the same time, it is necessary to construct a square matrix for channel allocation;

In the 8th step, the second time slot power distribution, the transmission power of the secondary user transmitter ST1 _" to the secondary user receiver in the second time slot is as follows:

in Represent the occupancy of channel n by the secondary user transmitter ST ₁ in the second time slot, and equally utilize the water filling algorithm to obtain the power allocated by the secondary user transmitter in this time slot on each channel;

Step 9: Perform resource allocation according to channel allocation and power allocation of the two time slots, and complete data transmission.

The cooperative multi-relay cognitive network of this embodiment is simulated. The simulation results show that the multi-relay cooperative scheme of this case can select relays and perform channel allocation and power allocation according to the rate requirements and channel conditions of the primary user, and finally realize secondary The capacity of the user network is maximized.

In addition to the above-mentioned embodiments, the present invention can also have other implementations. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims (2)

1. A cooperative multi-relay cognitive wireless network spectrum allocation method, comprising the steps of: Step 1, network system configuration, in the cooperative multi-relay cognitive network, there is a primary user transmitter PT, a primary user receiver PR, and L secondary user pairs, and each secondary user pair is controlled by the secondary user transmitter ST and the secondary user receiver SR, the set is represented by L, the normalized spectral bandwidth of the multi-relay cognitive network is B, the number of sub-channels is N, and the set of sub-channels is N, then the sub-channel bandwidth B ₀ =B/N , the secondary user uses adaptive modulation for data transmission, and the data transmission rate is automatically adjusted according to the quality of the channel; Step 2, system parameter setting, under this system, the transmission power of the primary user transmitter PT on each sub-channel is a fixed value P _pu , the total transmission power of the secondary user system is P _su , the primary user transmitter PT and the secondary user system The channel gains on channel n between the user transmitter ST, the secondary user transmitter ST and the primary user receiver PR, and the secondary user transmitter ST and the secondary user receiver SR are defined as with The channel noise has a mean of 0 and a variance of Gaussian white noise, the target rate of the primary user is R _T ; Step 3, relay selection and channel allocation, the specific steps are as follows: a1. Calculate the communication rate between the primary user transmitter PT and the secondary user transmitter ST _l on the nth channel Its calculation is as follows: Define the ratio of the communication rate of the primary user and the secondary user transmitter ST _l on the nth channel to the target rate of the primary user as the performance evaluation parameter for relay selection and channel allocation: Thus, the performance evaluation parameter matrix of the relay cognitive wireless network is obtained: Define parameter β _sum = 0; a2. Select the maximum value in the performance evaluation parameter matrix The corresponding secondary user is used as the optimal relay, and the corresponding channel is used as the optimal channel, that is, the primary user selects ST _l' as the relay and occupies channel n' for data transmission; a3. Update β _sum , Since a channel can only be occupied by one user at a time, the optimal channel n' no longer participates in the following secondary user channel selection, that is, a4. Cycle a2 and a3 until β _sum ≥ 1, that is, meet the primary user rate requirement; Step 4, sub-channel allocation of the first time slot. In step 3, the primary user can release the unoccupied channel under the condition of satisfying its own rate requirements, and the secondary user can occupy the channel not occupied by the primary user for data processing. Transmission, under this allocation method, in order to reflect the fairness among users, only the relay secondary users participating in the cooperation are allowed to occupy the remaining channels for their own data transmission in the first time slot. Assuming that the relay set is L*, the number of is L*, and the set of remaining channels is The number is The corresponding channel gain matrix can be expressed as Define the performance parameters of the l ^* th secondary user pair: The performance matrix can be obtained as follows: Use the Hungarian algorithm to obtain the optimal channel allocation scheme. Since the Hungarian algorithm solves the square matrix problem, when the remaining channels and the number of users are different, a square matrix needs to be constructed. At this time, there are two situations: b1. When the number of remaining channels is less than the number of users, a virtual channel needs to be constructed, and the channel gain is set to 0, namely: b2. When the number of remaining channels is greater than the number of users, it is necessary to construct virtual users. The maximum number of channels that each user may occupy is The performance matrix is constructed as follows: The 5th step, the first timeslot power distribution, according to the number of remaining channels occupied by each relay distribution transmission power, the secondary user transmitter The power is divided as follows: in, Indicates the occupancy of the channel n by the secondary user transmitter ST ₁ in the first time slot. When it is occupied, the value is 1, otherwise it is 0. Use the water filling algorithm to calculate the power of the secondary user transmitter participating in the relay on each occupied channel distribute; Step 6, in the second time slot, the secondary user transmitter acting as a relay forwards the primary user data to the primary user receiver, and all secondary user transmitters send their own transmission data to the secondary user receiver. 2. The cooperative multi-relay cognitive wireless network spectrum allocation method according to claim 1, characterized in that: the sixth step specifically comprises the following steps: c1. In the second time slot, the channel for forwarding the primary user signal is selected and the transmission power of the occupied channel is allocated. The channel for the relay forwarding the primary user signal can be the same as that of the primary user in the first time slot to the relay node The channels for transmitting signals are different. In the first time slot, the secondary user transmitter that is preferentially selected as the relay has the priority to select the channel n" with the largest channel gain as the channel occupied when transmitting the signal to the primary user receiver PR in the second time slot. , calculate the transmission power required by the secondary user transmitter ST _l* as a relay to forward the primary user in the second time slot c2, the second time slot channel allocation, in this time slot, each user transmitter can occupy the idle sub-channel, also use the Hungarian algorithm to obtain the optimal channel allocation scheme, and when the number of channels is different from the number of users, It is necessary to construct a square matrix for channel allocation; c3, the power distribution of the second time slot, the transmission power of the secondary user transmitter ST1 _" to the secondary user receiver in the second time slot is as follows: in Represent the occupancy of channel n by the secondary user transmitter ST ₁ in the second time slot, and equally utilize the water filling algorithm to obtain the power allocated by the secondary user transmitter in this time slot on each channel; c4. Perform resource allocation according to channel and power allocation conditions of the two time slots, and complete data transmission.